The invention relates generally to a method and an apparatus for fixing a location in an examination field, in particular in a surgical operating field. In particular, the invention relates also to obtaining data dependent upon the fixed location as well as displaying such data for a user.
U.S. Pat. No. 5,795,295 discloses a surgical microscope comprising an optical coherence tomography (OCT) apparatus with which a surgeon who observes an examination field through the microscope can obtain additional data from the operating field, the data being then displayed on a monitor. Moreover, it is known to obtain additional data from the examination field by means of an X-ray imaging device, an X-ray tomography device (CT) or a nuclear magnetic resonance tomography device (NMR).
In tomography systems known in the art a location within an examination field is fixed or identified, respectively, with respect to a coordinate system. After the location has been fixed, further determinations, examinations or tasks are carried out on the basis of the fixed location. A problem may exist in that the examination field moves relative to the coordinate system, or a field of view of a user observing the examination field moves relative to the coordinate system, so that, after such movement, coordinates of the fixed or identified location are no longer readily determinable.
One aspect of the invention is a method for fixing the position of a first location with respect to a coordinate system of an examining field. First, coordinates of the location to be fixed in the examination field are obtained as a set of coordinates which is allocated to the location to be fixed. A user identifies the location to be fixed in that the user views the examination field, in certain embodiments, through a microscope and aligns the location with respect to the examination field such that the location to be fixed is positioned in a graticule or in the center of the field of view of the microscope. The user then, in some embodiments, makes a corresponding input to the system which constitutes a request to the system determine the coordinates of the location within the examination field thus positioned in the center of the field of view. The coordinates determined are designated as a first coordinate set. Next, a first recording of topological data is obtained from a spatially extended area close to the identified location within the examination field. After a certain period of time has elapsed, a second recording of topological data of this area is obtained. If the examining field has been displaced relative to the coordinate system during that time, it is possible, by a comparison of the two recordings, to determine the magnitude of the displacement of the identified location with respect to the coordinate system. Next, the coordinates of the first coordinate set are changed, depending upon the determined displacement, such that the coordinates of the first coordinate set substantially correspond to the coordinates of the first location within the examination field after the displacement thereof. It is thus possible to track an identified location within the examination field such that after a displacement of the identified location has occurred, the latter need not be identified again.
In some embodiments, it is advantageous to periodically obtain further recordings of topological data and to determine a current displacement of the identified location with respect to the coordinate system by a comparison of the obtained recordings and to change the coordinates of the coordinate set such that these coordinates indicate the current coordinates of the identified location in the examination field.
In order to identify the location to be fixed, in some embodiments, the user may view the examination field directly, i.e., with the naked eye. In other embodiments, the user may use an imaging device to view the examination field. The imaging device in some embodiments includes a camera and a visual display unit, or a microscope or spectacles, in particular a binocular loupe.
In order to identify the location, in some embodiments a pointer is advantageously provided. The pointer includes a pointer tip which can be contacted by the user at the identified location. Moreover, in such embodiments a position detecting apparatus for determining the position of the pointer tip with respect to the coordinate system is included.
If the user employs an imaging device, some embodiments advantageously include, in addition, a marker which the user may bring into coincidence in the imaging device field of view with the location to be identified in order to identify the same. For example, this marker may be a marking, such as a graticule, which is fixedly positioned in the field of view of the imaging device, or the marker can be displaced by the user in the field of view of the imaging device.
Advantageously, some embodiments include a sightline detecting device or eye-tracker which detects the sightline of the user on basis of an eye position of the user, so that the user can simply identify the location to be fixed by his eye position, i.e., the sightline.
In the embodiments described herein, for the identification of the location to be fixed, the coordinates of the identified location are incorporated in the coordinate set upon a corresponding request made by the user. The user can make this request, for example, by actuating an electrical or mechanical switch, such as a foot-switch, by a voice command or by an eye movement.
After the location to be fixed has been identified, the user may give his attention to other tasks. The identified location is tracked even if it is displaced, in that the coordinate set is changed such that its coordinates substantially correspond to the coordinates of the identified location. In this respect, in some embodiments it is also possible to supply the coordinate set to a data recording apparatus which performs measurements at the location indicated by the coordinate set, i.e., substantially at the identified location, in order to determine at least one magnitude which is correlated with the examination field and is advantageously displayed in the field of view of the user.
Moreover, in some embodiments it is possible to identify, after the first location referred to above is identified, one or more further locations within the examination field and, if desired, to track the one or more further locations as well by means of recordings of topological data and corresponding displacements. An advantageous application of the invention resides in that the determined magnitude incorporates a value which indicates a distance between two identified locations.
Furthermore, in some embodiments it is advantageous for the at least one determined magnitude to incorporate a data set which is obtained from a plurality of measurements performed along a connecting line between two identified locations. This data set may, for example, comprise a depth profile of the examination field taken along the connecting line or a cross-section which is obtained by means of a three-dimensional imaging method, such as computer tomography. In some embodiments, these are advantageously displayed in the field of view of the user as well.
Advantageously, in some embodiments the topological data comprise coordinates of a plurality of surface points within the examination field which are obtainable, for example, by means of laser triangulation or the like. It is also possible to obtain the recordings of topological data by means of a camera, such as a CCD camera, and to compare these recordings to determine the displacement of the location in the examination field.
Moreover, in some embodiments it is also advantageous to use as topological data measuring data which are obtained from points below the surface of the examination field. Such data may, for example, be obtained by means of optical coherence tomography (OCT) or X-ray computer tomography (CT) or nuclear magnetic resonance tomography (NMR) or the like.
A further aspect of the invention provides an apparatus for displaying a magnitude obtained from within an examination field. The magnitude is to be displayed when determined at a location within the examination field which has been previously identified by a user, in the surroundings of such a location or dependent upon such a location. In one embodiment, the user can determine the location to be identified with his eyes by means of a sightline detecting apparatus for determining the eye position of the user. The magnitude to be determined in connection with the identified location is then detected by the apparatus and is displayed in the field of view of the user such that both the display of the magnitude and the examination field as such are in the field of view of the user at the same time. On the one hand, this enables a particularly simple identification of the location in the examination field by the user and, on the other hand, the user can perceive the magnitude measured at the identified location in his field of view without having to turn his eyes away from the examination field, for example, to a conventional display of the measuring value on monitor screen provided outside of the examination field. To this end, in some embodiments the display of the magnitude is advantageously faded into the beam path of a display device such as a microscope or a binocular loupe which the user employs to view the examination field.
In some embodiments, a position detecting device is advantageously provided in order to detect the position of the binocular loupe or the microscope with respect to the coordinate system, so that the coordinates of the location to which the user""s eyes are directed can be determined as well by the sightline detecting device.